The present invention relates to a bag mounted with casters, and especially to a bag having a vertically extensible handle. The bag of the present invention is used in the broad meaning of suitcases and attache-cases.
Bags provided with casters and a freely extensible handle have already been developed and widely used. Many types of bags having this structure can be boarded on planes. For example, bags of this structure have been mentioned in the description of U.S. Pat. No. 4,995,487; Japanese Patent Publication No. 4-76686 issued Dec. 4, 1992; and Japanese Non-examined Utility Model Publications Nos. 57-179824 issued Nov. 15, 1982 and 63-131634 issued Aug. 29, 1988. The bags mentioned in these publications are provided with two casters mounted on one side of a bottom face as shown in FIG. 1. The short legs 2 are fixed on an opposite side of the bottom face. When the bag is in a vertical position, the casters 1 and the legs 2 are in contact with the floor. In this condition, because the legs 2 which do not turn are in contact with the floor, the bag can stand upright without moving. Further, to allow the bag to be pulled, an extensible handle 3 is provided at an upper face of the bag. The casters 1 are mounted on the same side of the bag as the handle 3, because the bag is pulled while in a slanted or tilted orientation. As shown in FIG. 1, the bag can be moved when it is titled and pulled by the handle 3. When the bag is titled, the casters 1 are in contact with the floor and the legs 2 are not in contact with the floor. When the handle 3 is pulled in this condition, the casters 1 freely turn so as to facilitate movement of the bag. However, with bags that move in this fashion, the casters 1 cannot sometimes be used in narrow places like in the aisles of a plane or in a crowded area. When the bag is moved with the casters 1, the width of the bag is wider, and the bag cannot be moved freely in the aisles between the seats in the cabin of a plane, or in crowded areas. When the casters 1 cannot be used, it is necessary to lift the bag and carry it by hand. When the bag is lifted and carried by hand, it is possible to move the bag in the direction shown by arrow A of FIG. 1 in order to prevent the widest dimension of the bag from extending transversely relative to the direction of travel.
The bag mounted with casters has a convenient structure allowing it to be moved easily. This is because even if the bag is heavy, it is easily pulled by rolling it on the casters. To solve the above-noted drawbacks of such bags, the present inventor has developed a bag having the structure shown in FIG. 2. The bag shown in FIG. 2 has casters 21 fixed at a lower face of the bag body 24. To allow the bag body 24 to be self-standing in an upright position, the casters 21 are mounted at the four corners of the lower face. A grip 23A of handle 23 is placed at the center of the upper face of the bag body 24. As shown in FIG. 2, the bag of this structure is not moved by tilting it from a vertical position. As shown by the arrow of the FIG. 2, the bag is moved while standing in a vertical posture. When it is moved in the direction shown by the arrow, it can be moved through a narrow area. For this reason, it can be conveniently moved in plane cabins or in crowded areas. Furthermore, by using four free swiveling casters 21 which allow movement in any direction, the bag can be moved while upright and freely in any direction. The upright bag does not transmit the weight of the bag to the handle 23. Therefore, even a fairly heavy bag can be easily moved.
The bag shown in the FIG. 2, using the four casters described herein, has the advantage that it can be easily moved. However, with a bag of this structure, because the grip of the handle is pushed and moved horizontally, a force is applied to the bag body 24 and will deform it like a parallelogram as shown by the dotted line of FIG. 3. Since the vertical rods 23B of the handle 23 are extended to a high level and because the grip 23A is pushed horizontally in order to move the bag, the bag body 24 is strained by a strong bending moment resulting in deformation of the bag. Furthermore, because the bag can be rolled on any type of surface, when the bag is not rolled smoothly due to the unevenness of the rolling surface, an even stronger deforming force is applied to the bag body 24. For this reason, the bag body 24 needs to be able to resist the deformation of parallelogram shape shown by the dotted line.
Also, in order to allow easy motion of the bag, it is important to make the bag as light as possible. Even with bags mounted with casters, there are steps etc. that do not allow movement of the bag on the casters. In the places where the bag cannot be moved on the casters, it is necessary to lift the bag. For this reason, it is important to make the overall weight of the bag lighter to permit easy lifting. However, when the bag is made lighter, its mechanical resistance is reduced. For example, in order to effect a weight reduction, bags are often constructed by sewing cloth or plastic sheets, and therefore, the bags need to be partially reinforced because the material itself does not have sufficient strength to resist deformation. When is the bag is moved by pushing the grip horizontally, the bag needs to be reinforced by adding flat steel strips around the bag body to prevent parallelogram shape deformation of the bag body. Furthermore, bags made with hard paper, plastic sheets or metallic sheets, need thick and strong material to be used to prevent the parallelogram shape deformation. For this reason it is very difficult to make an overall light weight bag which can be moved while standing in an upright posture.
Further, an upright bag moving on casters needs a certain thickness to allow the bag to stand in a stable upright position. Particularly thin bags cannot stand upright and are unstable even with casters fixed at the four corners. This is because the casters of both sides are too close together. It is therefore always necessary to hold the grip of the bags which have little or no upright stability in order to prevent the bag from falling. Bags which are self-standing in an upright position are very convenient because they stand upright and are stable even if the grip is released. Thus, since it is not necessary to prevent the falling of the bag by holding the grip, the bag can be easily moved on the casters by pushing the grip horizontally. The drawback of the bag of this structure is that the body of the bag is made thicker, and gets deeper which in turns makes it inconvenient to insert and remove items at the bottom of the bag because the items placed at the top hinder the removal of the bottom items.
The present invention has been developed with the purpose to also solve this drawback, and an important object of the present invention is to provide a bag with a light bag body, which resists deformation when moved on the casters, and allows easy access to items placed inside the bag.
The above and further objects and features of the present invention will be more fully apparent from the following detailed description along with the accompanying drawings.